Support AMRs with different arrity

[zmedelis]

Let's say I want to generate two sentences with the same meaning (same AMR):

1. Apple is red
2. Apple has a red color

This can be implemented in a single HasProperty AMR and it currently works generating good sentences:

If I do not specify the property kind argument, I'd still expect the first "Apple is red" version to be generated. Currently, this does not work.

[rokasramas]

As a temporary solution, this can be achieved using IF block inside AMR that checks if "property kind" variable is defined on the optional frame: